1. Technical Field
An optoelectronic semiconductor device is disclosed, especially related to a layout of an electrode structure of the optoelectronic semiconductor device.
2. Reference to Related Application
This application claims the right of priority based on TW application Ser. No. 097146075, filed Nov. 26, 2008, entitled “OPTOELECTRONIC SEMICONDUCTOR DEVICE”, and the contents of which are incorporated herein by reference.
3. Description of the Related Art
The current crowding effect refers to an uneven distribution of current density occurred commonly in conventional light emitting devices. It accumulates heat locally in the lighting device and decreases the lighting efficiency. For the worse case, it damages the lighting device.
The layout of the electrode structure of the light emitting device is for the purpose of spreading the current driving into the semiconductor layer more evenly and solving the issue of current crowding. The key factors for consideration are the distance of the p-type electrode and the n-type electrode, and the positions of the pads and the fingers. However, as the chip size and the driving voltage of the light emitting device increases, the current flow to the end side of the finger is influenced by the accumulated resistance and therefore is not spread uniformly.
The layout of the electrode structure of the vertical type chip has the n-type electrode and the p-type electrode positioned in the opposite sides of the chip. But in this design, the epitaxial substrate needs to be removed to expose the first conductivity type semiconductor layer connected to the substrate so the first electrode can be formed on the exposed surface. Besides, a reflecting layer, a second electrode and a permanent substrate are formed on the second conductivity type semiconductor layer of the surface of the epitaxial structure. The process is complicated so it is difficult to maintain the yield and the cost is high.